Ok thanks for the help in advance... I "accidentially" upgraded to 3.1.3 a month ago or so, after successful Blackra1n and many months of customization, etc. I was mortified. I followed the steps I found here to download the 3.1.2 software , put the phone into DFU? mode was it, change my hosts file and add the saurik server, etc. Then I got the error code, but rain Blackra1n, it made it rain and after rebooting, Woohoo, I was running 3.1.2 jailbroken. But then i used Itunes and restored from my backup? I think, and it added all my old contacts, programs, etc, but after that sync, the actual cellular service stopped completely. No cell service, no phone calls, txt messages, internet, etc. My WIFI would work after I re-entered the network info and password, but no cell service. I spent HOURS googling for answers, searching here, nothing. I tried so many solutions, "Carrier file" searches, etc. no dice. After being without connectivity for 4 hours I was forced to "restore" my "backup" and "Upgrade' BACK to 3.1.3 and lost my jailbreak but got my contacts, programs, and cell service back. Can anyone explain to me how I could successfully go back to 3.1.2 and jailbreak and have my cell phone and 3G data actually work? Thank you very much in advance. EDIT: I am told that despite the fact I had one of the original brand new 3GS's with the desirable "Bootrom?" and therefore easily "unlocked" for using with the other carrier in the US? (is it sprint or tmobile?) and now I have "upgraded/updated" my bootrom band and am no longer unlockable, that is fine with me I am on ATT and plan on staying for the duration , so unlock is not a big deal to me. Thanks.